This invention relates to a method of suppressing mist from oil-containing functional fluids suitable for single use applications, such as, for example, rock drill oils, agricultural spray oils, chain saw oils, ammonium nitrate fuel oil blasting agents, sheet metal drawing lubricants and the like. More particularly, this invention relates to the addition to single use oil-containing functional fluids, such as chain saw lubricating oil compositions, of a mist suppressing amount of a high molecular weight copolymer prepared from alpha-monoolefins having 3 to about 20 carbon atoms.
2. Prior Art
Oil-containing compositions used as lubricants for chain saws generally comprise a lubricating oil component and a tackifier component which is intended to prevent the compositions from misting or spattering off the end of the chain during use. Known chain saw lubricating compositions, as disclosed, for example, in U.S. Pat. No. 4,740,324, include such tackifying components as polyethylene glycol or polyacrylic amide, each having a molecular weight of 1 million or above, or colophonium-containing resins such as balsam resin obtained from terpentine balsam, root resin obtained by solvent extraction from root stocks, and tall resin obtained by fractional distillation of tall oil.
The use of an anti-mist additive in various other lubricating oil compositions has also been described. For example, U.S. Pat. Nos. 3,929,652 and 4,210,544 relate to dual purpose cutting oils which serve as heavy duty cutting oils and machine lubricants and which comprise a base oil, an extreme pressure agent, a copper corrosion inhibitor and, preferably, a copolymer of ethylene and propylene as an anti-mist additive. Particularly preferred copolymer anti-mist additives are described as having a molecular weight ranging from about 70,000 to about 100,000 and a propylene content of from about 35 to about 50 percent.
British Patent 1,525,599 discloses a metal working lubricating oil composition which contains a major amount of an oil of lubricating viscosity, and a minor amount, sufficient to inhibit the composition from misting while in use, of at least one oil-soluble ethylene copolymer having a viscosity average molecular weight in the range from 130,000 to 250,000. The ethylene copolymer is derived from the copolymerization of ethylene and a heavier olefin selected from terminally unsaturated straight chain monoolefins containing from 3 to 12 carbon atoms, alpha-phenyl-1-alkenes containing 9 or 10 carbon atoms, 2-norbornene, terminally unsaturated non-conjugated di-olefins containing from 5 to 8 carbon atoms, dicyclopentadiene, 5-methylene-2-norbornene, and mixtures thereof. Preferably, the heavier olefin is propylene and the mole ratio of ethylene to the heavier olefin in the copolymer is in the range of from 1:3 to 3:1.
U.S. Pat. No. 3,919,098 relates to metal working compositions having improved low fog properties. The disclosed compositions comprise a major amount of a hydrocarbon oil and a minor amount of an antifog additive selected from polyisobutylene, poly-n-butene and mixtures thereof. The antifog additive is said to have a viscosity average molecular weight of from 0.3 to 10 million.
U.S. Pat. No. 3,805,918 relates to mist oil lubricating systems which pneumatically distribute fine droplets of an oil composition to the areas of various machine elements to be lubricated. The oil compositions described in this patent include a small amount of specified polyolefins to reduce the amount of stray mist during the lubrication process. The polyolefins which are disclosed are C.sub.2 C.sub.x copolymers of ethylene having a viscosity average molecular weight greater than 5,000. The polyolefins contain 40-80 molar percent ethylene, and the units defined as C.sub.x are derived from a C.sub.3 -C.sub.12 monoolefin. The preferred polyolefins are ethylene-propylene copolymers.
U.S. Pat. No. 4,105,569 relates to yarn finishes, particularly of the coning oil type, which comprise a viscosity index improper such as a polymethacrylate, a polyalkylstyrene, an ethylene-propylene copolymer or a polyisobutylene. The viscosity index improver provides better adherence of the finish to the yarn being treated, less propensity for dripping, and less finish "throw-off" during high speed winding of the treated yarn. The yarn finish formulations also contain a polysiloxane which functions to reduce surface tension of the finish and to prevent mist formation during high speed winding.
U.S. Pat. No. 4,400,281 relates to improving the adhesive and cohesive properties of a textile lubricating composition which contains mineral oil, fatty esters or natural oils and an emulsifying agent by adding to the textile lubricating composition 0.01-10 wt. % of a polymer having a molecular weight of 1-10 million and comprising either homopolymer of normal C.sub.6 -C.sub.4 alpha-monoolefins or copolymers of two or more normal C.sub.4 -C.sub.20 alpha-moolefins. Among the copolymers that may be added to the textile lubricating composition are copolymers of butene-1 and at least one C.sub.5 -C.sub.14 alpha-monoolefin such as hexene-1, octene-1, decene-1, dodecene-1 and/or tetradecene-1. The addition of the polymer improves the adherency of the lubricating composition without reducing its lubricity and reduces the tendency for the composition to sling.
U.S. Pat. No. 4,173,455 relates to aqueous diesel fuel emulsions which contain diesel fuel, a specified emulsifier, an antimisting agent, and water. The antimisting agent is added to the fuel emulsion to prevent the emulsion from atomizing on impact when a fuel container is ruptured. The antimist agent is supposed to cause the fuel emulsion to be expelled from the ruptured fuel container in "sheets" and "strings of beads" which do not provide sufficient surface area for explosive combustion. The antimisting agents to be used in the diesel fuel emulsion are described as longchain, high molecular weight polymers which were developed to improve flow of oil through pipelines. At column 3, lines 32-35 of this patent, it is stated that the antimisting agents that were used by the patentee were proprietary compositions purchased under the trade name of CDR or AM-1 (from Continental Oil Company) and that the composition of the antimisting agents was unknown. While the exact identity of the CDR or AM-1 polymer compositions is unknown to the applicants herein, it is believed that the compositions comprise homopolymers of octene-1.
U.S. Pat. Nos. 4,384,089 and 4,527,581 relate to the reduction of friction loss normally occurring in hydrocarbon carrying conduits during the transportation of hydrocarbon liquids can be reduced by adding small amounts of certain copolymers to the hydrocarbon liquids. The copolymers are described in U.S. Pat. No. 4,384,089 as comprising copolymers of two or more alpha-monoolefins having 3 to 20 carbon atoms, and in U.S. Pat. No. 4,527,581 as comprising copolymers of butene-1 and another alpha-monolefin having 5 to 20 carbon atoms. Neither of these patents suggests using the copolymers as anything other than hydrocarbon oil pipeline friction reducing agents.